Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $96.37   5.523%   $101.6925   $101.69   $101.70   $101.70  
  Purchase #2 $201.25   12.827%   $227.0643   $227.06   $227.05   $227.10  
  Purchase #3 $63.75   11.605%   $71.1482   $71.15   $71.15   $71.10  
  Purchase #4 $52.84   7.443%   $56.7729   $56.77   $56.75   $56.80  
  Purchase #5 $162.91   10.427%   $179.8966   $179.90   $179.90   $179.90  
  Purchase #6 $250.63   12.231%   $281.2846   $281.28   $281.30   $281.30  
  Purchase #7 $160.72   10.171%   $177.0668   $177.07   $177.05   $177.10  
  7 purchase totals = $988.47       $1,094.9259   $1,094.92   $1,094.90   $1,095.00